How does Blender Autodetect Texture Culture?
Blender's probably reading the instructions in the mtl (material library) file that accompanies the obj file.

According to the mtl specifications mtl files can include a parameter (-o) that instructs the program reading the file to reverse the texture's origin in the horizontal (u) or vertical (v) directions:

Quoting from the specification document:


  The -o option offsets the position of the texture map on the surface
  by shifting the position of the map origin. The default is 0, 0, 0. 
  
  "u" is the value for the horizontal direction of the texture 
  
  "v" is an optional argument.  "v" is the value for the vertical
  direction of the texture. 
  
  "w" is an optional argument.  "w" is the value used for the depth of a
  3D texture.


-o v   # This should reverse the texture's origin in the vertical direction


Open your OBJ's MTL files in a text editor and see if you can find anything that resembles this.